Recently, organic electroluminescent elements (hereinafter, referred to also as “organic EL elements”) have been used in various applications including lighting panels. An example of the organic EL element known is an EL element having a transparent substrate and a laminate of a transparent first electrode (anode), an multi-layered organic layer containing a light-emitting layer, and a second electrode (cathode) formed in that order on the surface of the transparent substrate, as described in JP-A No. 2005-108824. In organic EL elements, the light generated in the light-emitting layer when voltage is applied between the anode and the cathode passes through the transparent electrode and the substrate and is emitted outward.
Generally in organic EL elements, the intensity of the light from the light-emitting layer is decreased for example by absorption in the substrate and total reflection by an interface layer and thus, the intensity of the light withdrawn outward is smaller than the theoretical light intensity. Accordingly, there exists a need for improvement of the light-outcoupling efficiency of organic EL elements for improvement of brightness. It is known as a possible measure to form a light-outcoupling layer on the first electrode-sided surface of the transparent substrate for improvement of light-outcoupling efficiency. The light-outcoupling layer, when formed, reduces the total reflection at the interface between the substrate and the electrode and permits increase of the amount of the light emitted outward.
Since organic layers in organic EL elements are likely to be degraded by water, it is important to prevent penetration of water into the element. Degradation of an organic layer causes troubles such as insufficient light emission efficiency and thus deterioration of reliability of the organic EL element. Thus, for protection of the organic layer from water, a laminate containing an organic layer is normally covered and blocked from external environment by a covering material adhered to the transparent substrate. When a glass material is used as the transparent substrate and the sealing material, the glass material, which is resistant to water penetration, reduces penetration of water through the region. However, when a light-outcoupling layer for example of a plastic or resin material is formed on the surface of the transparent substrate for improvement of light-outcoupling efficiency, the plastic or resin material may cause a problem of penetration of water through the material because it is a material with relatively high water permeability.